EC-25 LTE: AT+QCFG="nwscanmode",3

I have an EC25 module with firmware EC25EFAR06A11M4G

I’m using a combination of

to restrict the modem to scanning in LTE only and on the whole, this is working very well.
However, on a few units, an
AT+QCFG=“nwscanmode”,3 write results in a read of
+QCFG: “nwscanmode”,0

So despite LTE bands being defined, the scan set to LTE (3) as the final write, the read defaults to auto (0) and LTE fails to work.
Neither GSM or UMTS have this issue.
The modem is used as part of a test system so we are programming the AT commands many times and changing RATs many times too. Any ideas as to why this might be happening?

Hello PG thanks for your question
If you want change RAT, you can execute at+qcfg=“nwscanmode” command, do not need execute at+qcfg=“band”, the command is used to specify the preferred frequency bands to be searched of UE.